This invention deals generally with heat exchangers and more specifically with a direct contact heat exchanger that transfers heat directly between fluids which are mixed together with each other.
Heat exchangers that transfer heat between two fluids are commonplace and well understood, and one inherent limitation they have is accepted and ignored because it is generally believed to be a necessity. In typical heat exchangers the two fluids are physically separated by a solid wall because it is accepted that they cannot be mixed. However, that solid wall limits the heat transfer between the fluids regardless of how high the thermal conductivity of its material is.
Vortex movement of two fluids has been used for both the mixing and separation of fluids, but only rarely in heat transfer. One known application using vortex flow for heat transfer between two fluids is the exchange of thermal energy between two high temperature (1200 to 3000 degrees F.) gases in which the lower temperature gas is injected tangentially into a chamber while the higher temperature gas is injected as axial flow along the central axis of the device. This inlet arrangement results in vortex flow with the two gas streams separated by a stagnation boundary. While some direct contact heat exchange occurs, solid particles which enter with the higher temperature gas provide the primary means of heat transport. As a result there is still an intermediate material transferring the heat. This device is described in Heat Exchanger Design Handbook by T. Kuppan, Marcel Dekker, Inc., New York, N.Y., pp. 340-341 (2000).
Since direct contact heat transfer eliminates the weight penalty of fins, walls, and tubing of heat conductive materials, it would be very beneficial to have a direct contact heat exchanger without any intermediate heat transfer material.